Optical networks are being deployed in interconnected mesh configurations using signaling and routing between network elements for establishing and maintaining sub network connections (SNCs). Conventionally, in optical networks, delay (i.e., latency) is measured indirectly via, administrative weights (“admin weights”), manually determined such as based on distance calculations, or to some extent derived using signaling message delays. There exists no known systems or methods to measure delay of lines (e.g., SNCs) in a non-intrusive and accurate manner. So, actual delay that is seen across hops (i.e., links in the network) is never measured and is not propagated to a routing database so that SNCs may be routed based on latency. There is no known method for two nodes or network elements that share a line to automatically establish who will make a measurement between them and who will participate and then have those measurements disseminated throughout the domain, so it may be used to route SNCs based on latency. Importantly, there is no on-demand delay discovery method for measuring the latency between two arbitrary end points in a domain in the network.